Bonneville America Forums Forums Technical Forums Performance Mods Big Bore jet size

I have recently fitted the Wiseco 904bb kit to my bike (04 TBA) and with the recent fair weather taken it out for a couple of rides. It has a Uni filter,no snorkels,TOR pipes and Thruxton needles. Main jets are 120 and pilots 42. Since the bb kit I have not changed anything. Plug colour is good and it goes really well but it does run a good bit hotter. Is this because it might be too lean and does fitting a bb kit mean that you need to up-jet?
I noticed on Pats calculator that there is no input for the bb kit. Anyone any thoughts on this?

I had done some carb work before the 904 kit. My dealer drilled the slides, put in a dyna kit needles and we ended up going down from the 130/45 I previously had to 125/45. After installing the BB kit and doing a few dyno runs, we tried going back up on the mains, but it proved to be best where we were.

I assume the TORs are not quite as open as the Specialty Spares. The bikes do run hot, but if the plugs look good and you're running fine, you are probably close. It at all possible it would be worth the time and money to do a dyno run and check the fuel/air mixture. It would show if you need to go up on the mains a bit. You didn't say if you had any excessive decel popping or where your pilot screws were. I went from the 42 to 45s to stop bad decel popping, but ended up with the pilot screws only two turns out where they had been at least 3 turns out.

I've burned 2 full tanks since the 904 install without changing the jets. Been checking the plugs, they seem to be OK. Uni filter, no snorkles, Bub pipes, one needle shim. Main jets are 122, stock pilots.

Thanks for the reply, a dyno is tricky as there are none within 300miles or so of where I live. As for popping on decel there is none at all! (3turns on pilots). The bike pulls really well so I think it must be close it was just the heat coming off it that worried me.

120 sounds really small. i would say 130 minimum with a shim or 2 on the needle. unless the tors dont flow much

Frank

I know its been beaten to death but your setup is close to mine and I am wondering if you felt a big difference in low end torque after the big bore or was it just a little more power?? Is it worth it to do?? I am been considering a secound bike in the v-twin form for the torque but Id rather just have the trumpet if I can get the powrer from it.. thanks

To me it was a HUGE difference. There is no more bang for the buck you could possibly do to the bike. Almost 30% more power and torque. I loved my bike, just wanted more oomph, especially starting off 2 up. It's like a whole different bike and I can't even tell the difference when my wife rides. It cost me a total of $1200. including labor. I would have paid way more than that for an optional more powerful version from Triumph.

The exhaust even sounds better as it is now slightly lower pitched. There's not a bike in the Triumph line I would rather have right now - including the newer models. I was considering the new mystery mid sized cruiser, but not anymore. I don't really want a radiator in front of my "classic" cruiser.

best money i spent on the bike. the dyno did not tell the truth for me, but there was a ton more tq than before and my buddies 100ci vic stays within site unlike before so i think it made a lil difference.

Frank